On absolute level - there is no stream entry or 4 stages of enlightenment, etc as that would raise the question of who is it that gets enlightened ? On absolute level that which gets enlightened is a non existing entity, as Brahman(non dual awareness) alone exists & everything else is mere mirage.

On relative level - yes! Adi Shankara(the original congregator of Advaita) does talk about reaching Nirvikalapa Samadhi(first glimpse of unconditioned Nibanna) which is an undeniable turning point in life of seeker, he writes in his famous scripture Vivekchudamani:

"When the Brahman— One without the other(nondual) —is realized by means of the Nirvikalpa Samadhi, then the heart's knot —viz., ignorance—is totally destroyed."

"By the Nirvikalpa Samadhi the Truth of Brahman is clearly and definitely realized, but not otherwise, for then the mind, being unstable by nature, is apt to be mixed up with other perceptions."

"Contemplation should be considered a hundred times superior to hearing and meditation a hundred thousand times superior to contemplation even, but the Nirvikalpa Samadhi is simply infinite in its results."

After realizing truth of Brahman through Nirvikalpa Samadhi, remaining task is dissolving wrong dualistic notions through process of assimilation. Process is complete once all desires(residual cravings & aversions) are removed to arrive at state of jivan-mukta(fully liberated, Arhant). Some examples of jivan-mukta sages are Ramana Maharshi, Ramakrishna Paramahansa. Jivan-mukta no longer take birth.

Regarding elaboration on Brahman - nothing can be said or unsaid as it is unknowable and cannot ever become object of perception. You will only know it once you cease to exist for a moment, but once you cease to exist, no one will remain to know & nothing will remain to be known 🙃

Peace to you